GOALS FOR THE COMING YEAR: 1. CHO cell mutants deficient in phosphatidylinositol. The biochemistry will be further elucidated, including determination of the endogenous inositol pool, and the subcellular distribution of the phosphotidylglycerol that accumulates in these mutants. The possibility of bypassing the inositol auxotrophy with exogenous liposomes containing phosphatidylinositol will also be examined. 2. Isolation of other CHO cell lipid mutants. Attempts will be made to identify conditionally lethal strains unable to incorporate 14C-choline. This will be done using filter-paper autoradiography. Such mutants might be defective in the choline-phosphotransferase pathway leading to lecithin. In addition to the above, specific screening techniques will be developed to isolate variants defective in the glycerol-P acyltransferase, a key enzyme in de novo membrane lipid synthesis. 3. A study of the effects of cytidine analogs on lipid composition. Using the 2-dimensional chromatography system described above, we will examine the effects of cytidine analogs - such as cytosine arabinoside -on phospholipid composition. This may suggest additonal approaches to the isolation of mutants.